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National Geologic Map Database
Geologic Unit: Mud Lake
Map showing publication footprint
  • Usage in publication:
    • /Mud Lake Gray Shale Member
  • Modifications:
    • First used
  • Dominant lithology:
    • Shale
  • AAPG geologic province:
    • Michigan basin
Publication:

Dellapenna, T.M., Twynham, Marnie, and Harrison, W.B., III, 1991, New stratigraphic nomenclature for the Antrim Group, Michigan basin [abs.], IN Michigan; its geology and geologic resources; a second symposium, 1991; program and abstracts: Michigan Geological Survey, East Lansing, MI, March 14-15, 1991, p. 1991-1992.


Summary:

Previously defined Antrim Shale is here raised in rank to Antrim Group and divided into three formations (ascending): Antrim (revised), Ellsworth (revised) , and Sanilac (new) Formations. The Sanilac consists of black shales formerly included within the upper part of the Ellsworth Shale in western MI and upper black shales within the Antrim Shale of eastern MI. Ellsworth Formation (revised) consists of gray shales below the upper black shales of the former Ellsworth in western MI and the gray shales of the "Upper" or "Light" Antrim of eastern MI. The Antrim Formation [of this report] is composed of black and gray shales below the Ellsworth and includes the previously known Traverse Formation. Antrim Formation is subdivided into (ascending) Mud Lake Gray Shale Member (Traverse Formation), Charlton Black Shale Member (lower black shale), Crapo Creek Gray Shale Member (middle gray shale), and Chester Black Shale Member (upper black shale). [Usage of the Antrim in this proposal is in violation of the NACSN, 1983, Art. 19(g), and is not recommended.]

Source: GNU records (USGS DDS-6; Reston GNULEX).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).